The present invention relates to a bearing piece for a suspension element for a motor vehicle, acting as a pressure sensor for a fluid-controlled brake regulator.
Fluid-controlled brake regulators operated by the suspension of a vehicle are known. Patent GB-B-1,542,507, for example, describes, a system of this type. For satisfactory operation of these regulators, the pressure sensor must be simple, reliable and easy to install in the vehicle. U.S. Pat. No. 4,824,180 describes a sensor of this type having an annular pressure chamber receiving an annular piston which is displaced as a function of the force perceived by the bearing cup of the suspension spring.
U.S. Pat. No. 4,828,329 provides a device integrating a regulator arranged between the turns of the suspension spring and having a closed pressure chamber coaxial with the device. However, this device is extremely complex and therefore expensive and, in the event of escape of the fluid enclosed in the chamber, the regulator behaves in a manner which may be prejudicial to safety.
Although being entirely satisfactory, these known sensors only give information on the suspension spring load and are in particular ineffective for measuring the load on the wheel of a vehicle with trim correction, in particular integrated with the shock absorber.
In addition, these known pressure sensors all have another disadvantage. They have a leaktight chamber in which the hydraulic pressure is a function of the load supported by the suspension element, this element being formed from the suspension spring and/or from the shock absorber. When the vehicle goes over a protuberance in the road, the pressure in the leaktight chamber increases rapidly and then decreases rapidly, corresponding to the moment when the load is removed from the wheels. If the height of the protuberance is great and/or if the speed of the vehicle is high, the wheels may then momentarily leave the ground. The suspension element then works in traction, and the relative pressure in the leaktight chamber may be cancelled out and even become negative, which can be prejudicial on the one hand to the diaphragm closing the leaktight chamber and on the other hand to the operation of the brake regulator which is combined with it.